Imagine a CD with a storage capacity not of 650 MB but 650 million MB. Such a storage capacity is theoretically possible because of experiments using individual atoms to store data.

But do not expect it soon; the gap between theory and practice is wide.

In 1959, physicist Richard Feynman pointed out that all the words written in the history of the world could be contained in a cube of material one tenth of a millimetre wide - provided those words were written with atoms.

Now, scientists have done just that, creating an atomic-scale memory by using atoms of silicon in place of the 1s and 0s that computers use to store data.

Proof of concept

The research is reported in the journal Nanotechnology. Scientists say it represents a first crude step toward a practical storage device in which atoms represent bits of information.

"This is proof of concept of what Feynman was saying 40 years ago," says Franz Himpsel of the University of Wisconsin.

The memory created by Himpsel provides a storage density a million times greater than a CD-Rom.

Atoms may be among the smallest physical things that can be used to store binary data. The potential of their storage capacity is awesome. For example, a grain of sand contains about 10 million billion atoms.

Too slow

The new memory was made on a silicon surface by lifting out single silicon atoms with the tip of a scanning tunnelling microscope. The gaps left behind represent the bits of data storage.

Conventional data storage uses millions of atoms per bit.

But while theoretically it is possible to use single atoms as storage bits, in practice it may take decades to make a practical version of atomic memory.

This is because of the problems of working with individual atoms at room temperature and the data rate at which the information is laid down, and subsequently read out again, is far too slow to be of any use at the moment.

DNA data

Researchers say that an intriguing aspect of the latest work is that memory density is comparable to the way nature stores data in DNA molecules.

The Wisconsin atomic-scale silicon memory uses 20 atoms to store one bit of information, including the space around the single atom bits.

DNA uses 32 atoms to store information in one half of the chemical base pair that is the fundamental unit that makes up genetic information.

"Compared to conventional storage media, both DNA and the silicon surface excel by their storage density," says Himpsel.